The best way to learn proper English is to read news report, and watch news on TV. Watching TV shows is a great way to learn casual English, slang words, understand culture reference and humor. If you have already watched these shows then you may recall the words used in the following dialogs.

Penny started taking a CLASS.
She wrote a paper.
The Big Bang Theory Season 6, Episode 6

You must have done it really bad
to be the loser in your CLASS.
Money Heist Season 1, Episode 10

...but they made me a junior professor
and are requiring me to teach a CLASS.
The Big Bang Theory Season 8, Episode 2

You can get them removed early
but you have to take his CLASS.
The Big Bang Theory Season 2, Episode 7

Just taking a CLASS
at the Pasadena Community College.
The Big Bang Theory Season 6, Episode 6